You could plan it and go through with it and just not tell her. If you're with other people and have plans to check in with people when/where you can that aren't on the trip with you (obviously not your parents), it sounds reasonable. Why not cancel the trip back home? Because taking care of yourself would upset them? If you want to get away, there are other places (as you obviously know).

I could never drive from Alaska to the equator in one trip though. Too much climate/weather difference in too short a time period but hey, be prepped for anything that might happen, and have a good time. You don't need your parents' approval for everything.